View Full Version : Won't run if glow plug disconnected . . ?
I have a K&B .40 that has always run very well. The compression isn't great, but it has always run good. I flew it into the ground and had to take it apart to clean it up. It runs, good in fact, but only if the glow plug is connected to the battery. When I disonnect it - it quits. What would cause this?
bigboots1302
09-25-2008, 11:09 PM
i dont know much about nitro (im an electric offroad truck driver) but if i were u i would try a new glow plug
ringmasterjr
09-30-2008, 01:25 PM
If you have replaced the plug, check the compression. I don't have PSI numbers or even a way to test it but if you can turn it over easily by hand using only the prop shaft, you may not have enough compresstion to keep it running. If the engine suffered internal damage from grit ingested during the accident, you may be in need of a new piston and liner.
Savage04
09-30-2008, 03:44 PM
check the fuel mixture. i had the same prob with my o.s .46 and it was way too rich and it kept dying after i pulled to glow igniter off. try adjusting your mixture see if that works
jamesf
10-05-2008, 10:51 PM
Hi,
It is either the Glow plug or the fuel. Most likely the glow plug.
zueslilbuddy
10-05-2008, 10:57 PM
I had the same problem with my T-Maxx(I know not a plane but its nitro)
I went to a hotter glow plug and fuel with higher nitro content and never had the problem again.
It was even running cooler.
Mark R
10-10-2008, 10:27 AM
3 things worth checking out have pretty much been covered. I would do this in order if I was having the same problem.
1) Change glow plug.... usually the number 1 cause
2) Rich air mixture, usually we can tell if an engine appear rich by a drop in RPM when the ignitor is removed, in your case the rpm drop may stall the engine.
3) Make sure fuel is good. I can't say how many times that older fual has caused similar problems for me.
Good luck!
tandemairbike
10-16-2008, 05:21 PM
If your K&B is an older model, I think it would be model 8011, and it seems to have little compression don't rush to install a new piston and liner. These engines have a Dykes pattern piston ring that only seals completely upon combustion. I have owned several of these over the years and they are fine engines even if the prop turns over after the engine quits in the air.
Hope this info is helpful.
Tandy
That is helpful. I didn't know about this sealing under comopression business, but it makes sense. I though this motor was worn out, but it keeps running, and it has more power than an OS .40 with good compression that I am running on another plane. I am having problems keeping it running though. It seems that the only way it will keep running is if I run it too rich - but then it loads up and just isn't smooth. I think the o-rings are worn out and its getting too much air. Where do I get replacement o-rings for that engine? What do you think? Thanks.
tandemairbike
10-18-2008, 07:28 PM
If you have a discount store near you that sells tools and hardware (mostly made in China) they will probably have an O ring assortment for about $7.00.
I am sure that there will be a size that fits. If you don't have a store like that near you go to <harborfreight.com>. They should have one in the same price range.
You might also take your old O ring to a hardware store and see if they can match it up.
Before you do that though, check to make sure the backplate is tight.
Good luck.
Thanks. That is xactly what I did. Haven't tried it out yet though.